Some 100,000 trees have been destroyed in the UK, where East Anglia has been particularly badly affected.

The infection has affected some 90% of ash trees in Denmark.

Ministers are concerned that the fungus could be present on fallen leaves and could be transferred via leaf mould.

Mr Paterson told the BBC: "Everyone should be responsible and if they do visit a wood just make sure they wash their boots, wash their dog, whatever's been running around the leaves, wash their child, to make sure they don't transfer to the next wood."

About 2,500 10sq km sites across the UK are being surveyed to establish how far the disease has spread, according to the Department for Environment, Food and Rural Affairs (Defra).

Amid criticism from Labour, Mr Paterson denied the government had been slow to act when the infection was first discovered.

He said: "This disease was only established here on 7 March. During the summer, trees are not planted so a programme of inspection has gone on during which 100,000 trees have been destroyed.

"But as I have also made clear, this disease as we discovered recently has possibly blown in.

Experts are urging people to report suspected cases of dieback in order to prevent the spread of the disease to the wider environment becoming established.

An app, Ashtag, has been launched to try to map the spread of the disease by allowing users to upload pictures and report possible sightings to a team which will pass any information to the Forestry Commission.